JP3645436B2 - Evaporative fuel treatment device leak diagnosis device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leak diagnosis apparatus for a fuel vapor processing apparatus for an internal combustion engine for automobiles.
[0002]
[Prior art]
In a conventional evaporative fuel processing apparatus for an internal combustion engine, evaporative fuel generated in a fuel tank is guided to a canister and temporarily adsorbed, and evaporative fuel adsorbed on the canister is introduced from a fresh air inlet of the canister. At the same time, the fuel is sucked into the intake system of the internal combustion engine through the purge control valve to prevent the evaporated fuel from being released into the atmosphere (see Japanese Patent Laid-Open No. 5-215020 etc.).
[0003]
By the way, in the above apparatus, if cracks occur in the piping of the purge line from the fuel tank through the canister to the purge control valve, or if a seal failure occurs at the joint of the piping, evaporative fuel leaks, It will not be possible to fully exert the effect of preventing radiation.
[0004]
Therefore, the following method has been considered as a leak diagnosis device for diagnosing the presence or absence of a leak of evaporated fuel from the purge line (see Japanese Patent Application No. 10-147338, etc.).
A switching valve that selectively connects the fresh air inlet of the canister to the atmosphere opening port and a discharge port of the electric air pump, and a fresh air inlet of the canister that bypasses the switching valve from the discharge port of the air pump. Thus, a bypass passage having a reference orifice having a reference diameter is provided.
[0005]
After the engine stops, first, the air pump is turned ON, the switching valve is switched to the atmosphere opening port side, the air pumped from the air pump is routed through the reference orifice of the bypass passage, and then the atmosphere is released from the atmosphere opening port through the switching valve. In the open state, the operating current value of the air pump is measured as a judgment level.
[0006]
Next, while the air pump is turned on, the switching valve is switched to the air pump side, and the air pump operating current value is supplied to the purge line from the fresh air inlet of the canister via the switching valve. Measure as leak level. Then, this leak level is compared with the determination level, and when the leak level is smaller than the determination level, it is diagnosed that there is a leak.
[0007]
According to this method, even when a small amount of leak occurs such as when a fine hole is generated in the pipe, it is possible to make a diagnosis with high accuracy.
[0008]
[Problems to be solved by the invention]
However, in the above method, the operating current value of the air pump stabilizes quickly and can be measured in a short time when the judgment level is measured, but when the leak level is measured, the leak and the air supply amount reach an equilibrium state. Otherwise, since the operating current value of the air pump is not stable and the capacity of the purge line is large, it takes time until the operating current value of the air pump is stabilized, so it is difficult to make an accurate diagnosis in a short time. There was a problem that.
[0009]
In view of such problems, an object of the present invention is to provide a leak diagnosis apparatus for an evaporative fuel processing apparatus that can shorten the diagnosis time without lowering the diagnosis accuracy.
[0010]
[Means for Solving the Problems]
The present invention introduces a vapor control fuel from a fuel tank to a canister having a fresh air inlet, temporarily adsorbs the fuel, and a purge control valve together with the fresh air introduced from the fresh air inlet. In the evaporative fuel processing apparatus for sucking into the intake system of the internal combustion engine via the engine, the leak diagnosis apparatus diagnoses the evaporative fuel leak from the purge line from the fuel tank through the canister to the purge control valve after the engine is stopped. Assumption.
[0011]
Here, in the invention according to claim 1, the leak level is measured by measuring the rate of change of the operating current value of the air pump when air is pumped to the purge line via the fresh air inlet by the electric air pump. Measure and predict the stabilized operating current value from the rate of change, and determine whether there is a leak by comparing the leak level with a predetermined determination level by using a leak level measurement means that uses the predicted value as a leak level And a leak determination means.
[0012]
According to a second aspect of the present invention, there is provided a switching valve for selectively connecting the fresh air inlet of the canister to the atmosphere opening port and the discharge port of the electric air pump, and bypassing the switch valve from the discharge port of the air pump. A bypass passage in which a reference orifice having a reference diameter is provided, and turning on the air pump, and switching the switching valve to the atmosphere opening side, Judgment level measurement that measures the air pump operating current value as a judgment level in a state where the air pumped from the air pump passes through the reference orifice of the bypass passage and then opens to the atmosphere through the switching valve. And the air pump is turned ON, the switching valve is switched to the air pump side, and the air fed from the air pump is sent to the switching valve. While supplying the purge line from the fresh air inlet of the canister through the rate of change of the operating current value of the air pump is measured, by predicting the operating current value after stabilizing the said alteration rate, the prediction value Leak level measurement means for setting a leak level and leak determination means for comparing the leak level with the determination level to determine the presence or absence of a leak are provided.
[0013]
In the invention according to claim 3 , in the invention according to claim 1 or claim 2 , the leak level measuring means measures the operating current value of the air pump at two points of a predetermined time interval, and based on the difference The rate of change is calculated.
[0014]
【The invention's effect】
According to the first aspect of the present invention, since the operating current value after stabilization of the air pump at the time of leak level measurement and the rate of change of the initial operating current value are in a correspondence relationship, the operation of the air pump at the time of leak level measurement By measuring the leak level by measuring the rate of change of the current value, the diagnosis time can be shortened without reducing the diagnosis accuracy.
[0015]
In addition, by measuring the rate of change of the operating current value of the air pump, predicting the stabilized operating current value from the rate of change, and using the predicted value as the leak level, the previous determination level can be used as it is. it can.
[0016]
According to the invention of claim 2 , in addition to the effect of the invention of claim 1, the determination level can be made accurate, and the diagnostic accuracy can be improved.
[0017]
Also, when measuring the judgment level, the air pump operating current value is measured as the judgment level, and when the leak level is measured, the rate of change of the air pump operating current value is measured, and the stabilized operating current value is predicted from the rate of change. Thus, the leak value can be accurately determined by setting the predicted value as the leak level.
[0018]
According to the third aspect of the present invention, at the time of measuring the leak level, the operating current value of the air pump is measured at two points at a predetermined time interval, and the rate of change is calculated based on the difference between the measured values. It can be accurately captured.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a system diagram showing an embodiment of the present invention.
[0020]
A throttle valve 2 is provided in the intake system of the internal combustion engine 1, thereby controlling the intake air amount. Further, an electromagnetic fuel injection valve 4 is provided for each cylinder in the manifold portion of the intake pipe 3 downstream of the throttle valve 2. The fuel injection valve 4 is opened by a drive pulse signal output in synchronization with engine rotation from the control unit 20 to perform fuel injection, and the injected fuel is combusted in the combustion chamber of the engine 1.
[0021]
The evaporative fuel processing apparatus is provided with a canister 7 that guides the evaporative fuel generated in the fuel tank 5 through the evaporative fuel introduction passage 6 and temporarily adsorbs it. The canister 7 is a container filled with an adsorbent 8 such as activated carbon.
[0022]
The canister 7 is also formed with a fresh air inlet 9 and a purge passage 10 is led out. The purge passage 10 is connected to the intake pipe 3 downstream of the throttle valve 2 via a purge control valve 11. The purge control valve 11 is opened by a signal output from the control unit 20.
[0023]
Accordingly, the evaporated fuel generated in the fuel tank 5 while the engine 1 is stopped is guided to the canister 7 by the evaporated fuel introduction passage 6 and adsorbed thereto. When the engine 1 is started and a predetermined purge permission condition is satisfied, the purge control valve 11 is opened, and the intake negative pressure of the engine 1 acts on the canister 7, so that fresh air introduced from the fresh air inlet 9. The vaporized fuel adsorbed in the canister 7 is desorbed by this, and the purge gas containing the desorbed vaporized fuel is sucked into the intake pipe 3 through the purge passage 10 and then burned in the combustion chamber of the engine 1. Is done.
[0024]
As a leak diagnosis device for the evaporated fuel processing device, the following device is provided on the fresh air inlet 9 side of the canister 7.
An air release port 12 is provided, and an electric air pump 13 is provided. An electromagnetic switching valve 14 is provided for selectively connecting the fresh air inlet 9 of the canister 7 to the atmosphere opening 12 and the outlet 13 a of the air pump 13. A bypass passage 15 is provided from the discharge port 13a of the air pump 13 to the switching valve 14 to reach the fresh air introduction port 9 of the canister 7. The bypass passage 15 has a reference diameter (for example, 0.5 mm). An orifice 16 is provided. An air filter 17 is provided at the atmosphere opening 12 and the suction port 13 b of the air pump 13.
[0025]
The switching valve 14 is switched to the atmosphere opening 12 side in the OFF state and switched to the air pump 13 side in the ON state, and is normally switched to the atmosphere opening 12 side in the OFF state. 9 communicates with the atmosphere opening 12.
[0026]
The control unit 20 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, and signals are input from various sensors.
[0027]
The various sensors include a crank angle sensor 21 that can output a crank angle signal in synchronization with the rotation of the engine 1 and thereby detect the engine speed Ne, an air flow meter 22 that measures the intake air amount Qa, and an engine exhaust system. An air-fuel ratio sensor (oxygen sensor) 23 for detecting the air-fuel ratio, a vehicle speed sensor 24 for detecting the vehicle speed VSP, and the like, and a current sensor 25 for detecting the operating current value of the air pump 13 are further provided.
[0028]
Here, the control unit 20 controls the operation of the fuel injection valve 4 based on the engine operating condition, and controls the operation of the purge control valve 11 based on the engine operating condition. Further, after the engine is stopped, the operation of the air pump 13 and the switching valve 14 constituting the leak diagnosis device is controlled to perform a leak diagnosis of the evaporated fuel processing device.
[0029]
As shown in FIG. 2, the control unit 20 is provided with functions as determination level measurement means, leak level measurement means, and leak determination means in software for leak diagnosis of the evaporated fuel processing apparatus.
[0030]
Next, leak diagnosis of the evaporated fuel processing apparatus by the control unit 20 will be described with reference to the flowchart of FIG.
In step 1 (denoted as S1 in the figure, the same applies hereinafter), whether or not the following conditions (1) and (2) are all satisfied is determined as to whether or not the engine is in a predetermined diagnosis execution condition. Judge by.
[0031]
(1) Engine speed Ne ≦ predetermined value (2) Vehicle speed VSP ≦ predetermined value
If it is not after the engine is stopped, that is, if the engine is operating, the routine returns to step 1 and this determination is repeated.
[0032]
If the engine has stopped, the process proceeds to step 2 to execute a leak diagnosis. However, if the purge control valve 11 is diagnosed as having a failure in a separately executed failure diagnosis routine, the leak diagnosis may be canceled.
[0033]
In step 2, the purge line atmosphere is initialized. Specifically, (1) the purge control valve 11 is opened, (2) the switching valve 14 is turned OFF and switched to the atmosphere opening 12 side, and (3) the air pump 13 is turned ON. This state is maintained for a predetermined time.
[0034]
At this time, as shown in FIG. 4, the air sucked and discharged by the air pump 13 passes through the bypass passage 15, passes through the canister 7 from the fresh air inlet 9 of the canister 7, and enters the purge control valve 11 of the purge passage 10. After that, it flows into the intake pipe 3. A part of the air passes through the bypass passage 15 and then flows back through the switching valve 14 and is released into the atmosphere from the atmosphere opening port 12.
[0035]
As a result, the residual pressure (negative pressure) and residual gas in the purge passage 10 are removed.
Next, in step 3, the determination level for leak diagnosis is measured. Specifically, (1) the purge control valve 11 is closed, (2) the switching valve 14 is turned OFF and switched to the atmosphere opening 12 side, and (3) the air pump 13 is turned ON.
[0036]
At this time, as shown in FIG. 5, after the air sucked and discharged by the air pump 13 passes through the bypass passage 15 (reference orifice 16), the air flows backward through the switching valve 14 and is released into the atmosphere from the atmosphere opening port 12. .
[0037]
In this state, the operating current value of the air pump 13 is measured by the current sensor 25, and this is defined as ASL. That is, the operating current value ASL of the air pump 13 when the air pumped from the air pump 13 is released to the atmosphere via the reference orifice 16 having a reference diameter is measured and used as a determination level. This portion corresponds to a determination level measuring unit.
[0038]
Next, in step 4, the leak level is measured. Specifically, (1) the purge control valve 11 is closed, (2) the switching valve 14 is turned on and switched to the air pump 13 side, and (3) the air pump 13 is turned on.
[0039]
At this time, as shown in FIG. 6, the air sucked and discharged by the air pump 13 passes through the switching valve 14, passes through the canister 7 from the fresh air inlet 9 of the canister 7, and purges the control valve from the fuel tank 5 through the canister 7. 11 flows into the purge line (6, 10) leading to 11.
[0040]
In this state, the operating current value of the air pump 13 is measured by the current sensor 25, and this is defined as A1. Further, after a predetermined time, the operating current value of the air pump 13 is measured again by the current sensor 25, and this is defined as A2. That is, the operating current values A1 and A2 of the air pump 13 when the air pumped from the air pump 13 is supplied to the purge line are measured at two points at predetermined time intervals. And based on these, change rate (DELTA) A = A2-A1 of pump working current value is calculated. The rate of change is accurately expressed as ΔA = (A2−A1) / predetermined time. However, in order to simplify the processing, the predetermined time is constant and ΔA = A2−A1. Then, the pump operating current value AA = f (ΔA) after stabilization is predicted from the change rate ΔA = A2−A1 of the pump operating current value with reference to a table prepared in advance, and this is set as the leak level. . This part corresponds to the leak level measuring means.
[0041]
Next, in step 5, the leak level (predicted value of the pump operating current value after stabilization) AA measured in step 4 is compared with the determination level ASL measured and set in step 3, and evaporated fuel. Perform a leak diagnosis. That is, referring to FIG. 7, when it is determined that the stabilized operating current value (predicted value) AA is larger than the determination level, it is diagnosed that there is no leakage, but the stabilized operating current value (predicted value). When it is determined that AA is below the determination level (see AA ′), it is diagnosed that there is a leak, and a predetermined failure code is set in step 6. This part corresponds to a leak determination means.
[0042]
That is, the operating current value (predicted value) after stabilization at the time of the leak level measurement is compared with the operating current value of the air pump 13 required for the air pumped from the air pump 13 to flow through the reference orifice 16 having the reference diameter. When the air pump 13 is smaller, that is, when the driving load of the air pump 13 is reduced, the purge line (6, 10) causes a failure equivalent to the opening of the hole larger than the reference diameter, and the leak exceeds the determination level. If this is not the case, diagnose that there is no leak (normal).
[0043]
Here, since the pump operating current value after stabilization at the time of leak level measurement and the rate of change of the initial pump operating current value have a corresponding relationship, the rate of change ΔA of the pump operating current value is measured at the time of leak level measurement. Thus, by predicting the stabilized pump operating current value AA, the diagnosis time can be shortened without reducing the diagnosis accuracy.
[0044]
In the above embodiment, in order to improve diagnosis accuracy, the determination level for the stabilized pump operating current value predicted from the rate of change of the pump operating current value as the leak level is set by measurement. The determination level may be set as a constant.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing a leak diagnosis function of a control unit. FIG. 3 is a leak diagnosis flowchart. [Fig. 5] Diagram showing air flow during determination level measurement [Fig. 6] Diagram showing air flow during leak level measurement [Fig. 7] Diagram showing pump operating current value during leak level measurement [Fig. Explanation of symbols]
1 Internal combustion engine
2 Throttle valve
3 Intake pipe
4 Fuel injection valve
5 Fuel tank
6 Evaporative fuel introduction passage
7 Canister
8 Adsorbent
9 Fresh air inlet
10 Purge passage
11 Purge control valve
12 Opening to the atmosphere
13 Air pump
14 Switching valve
15 Bypass passage
16 Reference orifice
17 Air filter
20 Control unit
21 Crank angle sensor
22 Air flow meter
23 Air-fuel ratio sensor
24 Vehicle speed sensor
25 Current sensor

Claims (3)

Evaporated fuel from the fuel tank is guided to a canister having a fresh air inlet and temporarily adsorbed, and the evaporated fuel adsorbed by the canister is injected into the internal combustion via a purge control valve together with fresh air introduced from the fresh air inlet. In the evaporative fuel processing apparatus to be sucked into the intake system of the engine, a leak diagnosis apparatus for diagnosing evaporative fuel leak from the purge line from the fuel tank to the purge control valve after stopping the engine,
Measure the rate of change of the operating current value of the air pump when air is pumped to the purge line via the fresh air inlet by an electric air pump, and predict the operating current value after stabilization from the rate of change, A leak level measuring means that uses the predicted value as a leak level ;
Leak determination means for comparing the leak level with a predetermined determination level to determine the presence or absence of a leak;
A leak diagnosis apparatus for an evaporated fuel processing apparatus, comprising: Evaporated fuel from the fuel tank is guided to a canister having a fresh air inlet and temporarily adsorbed, and the evaporated fuel adsorbed by the canister is injected into the internal combustion via a purge control valve together with fresh air introduced from the fresh air inlet. In the evaporative fuel processing apparatus to be sucked into the intake system of the engine, a leak diagnosis apparatus for diagnosing evaporative fuel leak from the purge line from the fuel tank to the purge control valve after stopping the engine,
A switching valve that selectively connects the fresh air inlet of the canister to the atmosphere opening port and a discharge port of the electric air pump, and a fresh air inlet of the canister that bypasses the switching valve from the discharge port of the air pump. And providing a bypass passage in which a reference orifice having a reference diameter is interposed,
The air pump is turned on, the switching valve is switched to the atmosphere opening side, the air pumped from the air pump is passed through the reference orifice of the bypass passage, and then the atmosphere is opened from the atmosphere opening port through the switching valve. In the opened state, determination level measuring means for measuring the operating current value of the air pump as a determination level;
The air pump is turned on, the switching valve is switched to the air pump side, and the air pumped is supplied to the purge line from the fresh air inlet of the canister via the switching valve. Leak level measurement means that measures the rate of change of the operating current value, predicts the stabilized operating current value from the rate of change, and sets the predicted value as the leak level ;
Leak determination means that compares the leak level with the determination level to determine whether there is a leak;
A leak diagnosis apparatus for an evaporated fuel processing apparatus, comprising: 3. The evaporation according to claim 1, wherein the leak level measuring unit measures an operating current value of the air pump at two points of a predetermined time interval, and calculates a change rate based on the difference. A leak diagnosis device for a fuel processor.

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